Well, they did say to be exact, and you handed them approximations, so...
I guarantee nothing in anyone’s time accounting system is measured to double-precision accuracy. Or at least, I’ve never quite figured out the knack myself for stopping work within a particular 6 picosecond window.
What's notable is clearly no one had actually thought this through at a policy level - the answer was "excel goes brrrr" depending on how they want to add up and subtotal things.